Native starch, i.e. starch recovered in its original form by extraction from any starch-bearing material, is a starting material for numerous valuable products. Starch hydrolysis process can yield glucose syrups, high maltose syrups, very high maltose syrups and the like. From these syrups, several products can be obtained such as crystalline dextrose, polyols and the like.
The process to hydrolyse starch typically comprises liquefaction and saccharification of native starch in the form of a starch slurry. Starch is a natural ingredient with a typical behaviour when it is put into suspension (starch slurry). Above a certain dry substance, the slurry is very difficult to treat and can be responsible for blocking processing equipment. Therefore in current processes, starch slurry to be liquefied typically has a dry substance up to 40 weight/weight % (w/w %) and preferably of from 30 to 35 w/w %. Taking into account heating via steam injection for the liquefaction and subsequent flashing for the saccharification, the liquefact thus produced also has a comparable dry substance. However it is desirable to increase this dry substance, for reasons of microbial stability, cost, process efficiency and the like. At least one additional concentration step, typically by evaporation, is necessary to bring the dry substance content of the produced glucose syrups to the desired value, such as for example 60 w/w %, 70 w/w %, 80 w/w %, 85 w/w %, etc. This concentration step usually requires a high energy input and is therefore not cost efficient and not environmentally friendly. In the effort to reduce energy consumption of industrial processes, there is a need to provide a more efficient process with significant lower energy consumption.
EP 0806434A1 describes a batch process for preparing enzyme converted starches.
U.S. Pat. No. 4,235,965 describes a batch process to hydrolyse starch, starting from a starch slurry having a dry substance of up to 40 w/w %. The process is a non-continuous batch process and requires very high amounts of enzymes, consequently the process is relatively inefficient and very costly.
There is thus a need for a starch liquefaction process with a higher capacity and better energy balance that preferably runs continuously. The present invention provides for such a starch liquefaction process.